#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
const int N = 1010;
int f[N][N];
int main()
{
    string s;
    cin >> s;
    int n = s.size();
    s = " " + s;
    for (int len = 2; len <= n; len++)
    {
        for (int i = 1; i + len - 1 <= n; i++)
        {
            int j = i + len - 1;
            if (s[i] == s[j])
            {
                f[i][j] = f[i + 1][j - 1];
            }
            else
            {
                f[i][j] = min(f[i + 1][j], f[i][j - 1]) + 1;
            }
        }
    }
    cout << f[1][n] << endl;
    return 0;
}